Apparatus to simulate biocide performance in crude pipeline conditions

ABSTRACT

An apparatus to simulate biocide performance in crude oil pipeline conditions is disclosed. The apparatus includes: a reactor to simulate a two-phase crude oil pipeline which includes a crude oil phase above a water phase. The reactor has an agitator to control a flow of the water phase in the reactor in response to a motor that drives an agitation rate of the agitator. A crude oil inlet supplies crude oil to the reactor for the crude oil phase. A water inlet supplies water to the reactor for the water phase. A control circuit is configured by code to control a proportion of the water to the crude oil supplied to the reactor and to control the motor to drive a desired agitation rate of the agitator. A biocide inlet supplies biocide to the reactor. A water sample outlet enables sampling of the water phase of the reactor.

FIELD OF THE DISCLOSURE

The present disclosure relates in general to crude pipeline simulationtechnologies, and in particular to an apparatus to simulate biocideperformance in crude pipeline conditions.

BACKGROUND OF THE DISCLOSURE

Crude oil (such as sweet crude, averaging less than 0.5% sulfur) isoften transported by a metallic pipeline. During the pipelinetransportation process, water and solids naturally present in the crudecan drop out of the solution and deposit or form a separate flow (e.g.,a two-phase flow) on the bottom of the pipeline's interior. These dropouts can accumulate at low points in the pipeline due to low flowvelocity or even stagnant flow. As such, the drop outs can become abreeding ground for corrosion, such as microbial corrosion, and othermicrobiologically influenced corrosion (MIC) effects in crude oilpipelines.

Uncontrolled microbial activity, and the consequent microbial corrosion,is one of the leading causes of pipeline failure in the oil industry.The processed crude oil normally only contains very low “basic sedimentand water” (BS&W) (such as less than 1%) as required by oil transmissionpipeline tariffs. This small amount of water, when kept off the pipelinewall and entrained in the crude oil, should not pose high microbialcorrosion risks to the crude pipelines. However, when oil productiondecreases, and as a consequence, the flow rate decreases in the crudepipelines, the trace water and sediments can drop out of the crude oiland accumulate at low-lying sections of the pipelines, causingunder-deposit corrosion and microbial corrosion.

It is in regard to these and other problems in the art that the presentdisclosure is directed to provide a technical solution for effectivesimulation of biocide and other oil field chemical treatment in crudepipeline conditions.

SUMMARY OF THE DISCLOSURE

According to an embodiment, an apparatus to simulate biocide performancein crude oil pipeline conditions is provided. The apparatus includes: areactor to simulate a two-phase crude oil pipeline and including a crudeoil phase above a water phase, the reactor including an agitator tocontrol a flow of the water phase in the reactor in response to a motorthat drives an agitation rate of the agitator; a crude oil inlet tosupply crude oil to the reactor for the crude oil phase; a water inletto supply water to the reactor for the water phase; a control circuitconfigured by logic or code to control a proportion of the water to thecrude oil supplied to the reactor by the crude oil inlet and the waterinlet, and to control the motor to drive a desired agitation rate of theagitator; a biocide inlet to supply biocide to the reactor; and a watersample outlet to sample the water phase of the reactor.

In an embodiment, the reactor further includes a plurality of reactorseach having a dedicated said biocide inlet and a dedicated said watersample outlet, and the control circuit is further configured by logic orcode to independently control the proportion of the water to the crudeoil and to independently control the motor in each reactor.

In an embodiment, the apparatus further includes: a crude oil pump topump the crude oil from a crude oil supply to the crude oil inlet; and awater pump to pump the water from a water supply to the water inlet,wherein the control circuit controls the proportion of the water to thecrude oil by controlling the crude oil pump and the water pump.

In an embodiment, the apparatus further includes a plurality of couponholders each configured to hold a corrosion coupon at a bottom of theagitated water phase of the reactor during a simulation, and to permitremoving and replacing of the corrosion coupon during the simulation.

In an embodiment, the apparatus further includes a ball valve for eachcoupon holder, the ball valve being configured to seal the reactorduring the removal and replacement of the corrosion coupon.

In an embodiment, the reactor further includes a bucket and the agitatorincludes a rotor at the bottom of the bucket, the agitation rate being arotation speed of the rotor, and the control circuit further controlsthe motor to adjust a height of the rotor above the bottom of thebucket.

In an embodiment, the apparatus further includes a height-adjustable diptube to obtain a mixed sample of the crude oil phase and the water phaseof the reactor at an interphase region of the crude oil phase and thewater phase in the reactor.

In an embodiment, the apparatus further includes a heating element toheat the reactor and a temperature sensor to sense a temperature of thereactor, wherein the control circuit is further configured by logic orcode to control the temperature of the reactor by using the temperaturesensor to sense the temperature of the reactor and by using the heatingelement to heat the reactor in response to the sensed temperature.

According to another embodiment, an apparatus to simulate oil fieldchemical performance in crude oil pipeline conditions is provided. Theapparatus includes: a plurality of reactors each configured to simulatea two-phase crude oil pipeline and including a crude oil phase above awater phase, each reactor including an agitator to control a flow of thewater phase in the reactor in response to a motor that drives anagitation rate of the agitator; a crude oil inlet to supply crude oil toeach reactor for the crude oil phase; a water inlet to supply water toeach reactor for the water phase; a control circuit configured by logicor code to independently control a proportion of the water to the crudeoil supplied to each reactor by the crude oil inlet and the water inlet,and to independently control the motor of each reactor to drive adesired agitation rate of the agitator of the reactor; a dedicated oilfield chemical inlet for each reactor to supply an oil field chemical tothe reactor; and a dedicated water sample outlet for each reactor tosample the water phase of the reactor.

In an embodiment, the oil field chemical includes at least one of acorrosion inhibitor and a biocide.

In an embodiment, the apparatus further includes: a crude oil pump topump the crude oil from a crude oil supply to the crude oil inlet; and awater pump to pump the water from a water supply to the water inlet,wherein the control circuit controls the proportion of the water to thecrude oil by controlling the crude oil pump and the water pump.

In an embodiment, each reactor further includes a plurality of couponholders each configured to hold a corrosion coupon at a bottom of theagitated water phase of the reactor during a simulation, and to permitremoving and replacing of the corrosion coupon during the simulation.

In an embodiment, the apparatus further includes a ball valve for eachcoupon holder, the ball valve being configured to seal the reactorduring the removal and replacement of the corrosion coupon.

In an embodiment, each reactor further includes a bucket and theagitator includes a rotor at the bottom of the bucket, the agitationrate being a rotation speed of the rotor, and the control circuitfurther controls the motor of each reactor to adjust a height of therotor above the bottom of the bucket of the reactor.

In an embodiment, the apparatus further includes a dedicatedheight-adjustable dip tube for each reactor to obtain a mixed sample ofthe crude oil phase and the water phase of the reactor at an interphaseregion of the crude oil phase and the water phase in the reactor.

In an embodiment, the apparatus further includes a dedicated heatingelement for each reactor to heat the reactor and a dedicated temperaturesensor for each reactor to sense a temperature of the reactor, whereinthe control circuit is further configured by logic or code toindependently control the temperature of each reactor by using thetemperature sensor to sense the temperature of the reactor and by usingthe heating element to heat the reactor in response to the sensedtemperature.

According to another embodiment, a method to simulate biocideperformance in crude oil pipeline conditions is provided. The methodincludes: simulating a two-phase crude oil pipeline in a reactorincluding a crude oil phase above a water phase; controlling, using aprocessing circuit, a flow of the water phase in the reactor bycontrolling a motor of an agitator to drive a desired agitation rate ofthe agitator to agitate the water phase; supplying, using the processingcircuit, crude oil to the reactor for the crude oil phase; supplying,using the processing circuit, water to the reactor for the water phaseto reach a desired proportion of the water to the crude oil supplied tothe reactor; supplying, through a biocide inlet, biocide to the reactor;and sampling, through a water sample outlet, the water phase of thereactor.

In an embodiment, the reactor further includes a plurality of reactors,controlling the flow of the water phase includes independentlycontrolling the flow of the water phase in each reactor by controllingthe motor of the agitator to drive the desired agitation rate of theagitator of the reactor, supplying the crude oil to the reactor includesindependently supplying the crude oil to each reactor, and supplying thewater to the reactor includes independently supplying the water to eachreactor to reach the desired proportion of the water to the crude oilsupplied to the reactor.

In an embodiment, the reactor further includes a plurality of reactorseach having a dedicated said biocide inlet and a dedicated said watersample outlet, supplying the biocide to the reactor includesindependently supplying, through the dedicated biocide inlet of eachreactor, the biocide to the reactor, and sampling the water phase of thereactor includes independently supplying, through the dedicated watersample outlet, the water phase of the reactor.

In an embodiment, the method further includes removing and replacing acorrosion coupon at a bottom of the agitated water phase of the reactorduring a simulation.

In an embodiment, the reactor further includes a bucket and the agitatorincludes a rotor at the bottom of the bucket, the agitation rate being arotation speed of the rotor, and controlling the motor further includescontrolling the motor to adjust a height of the rotor above the bottomof the bucket.

According to another embodiment, a method to simulate oil field chemicalperformance in crude oil pipeline conditions is provided. The apparatusincludes: independently simulating a two-phase crude oil pipeline ineach of a plurality of reactors each including a crude oil phase above awater phase; independently controlling, using a processing circuit, aflow of the water phase in each reactor by independently controlling amotor of an agitator of each reactor to drive a desired agitation rateof the agitator of the reactor to agitate the water phase of thereactor; independently supplying, using the processing circuit, crudeoil to each reactor for the crude oil phase of the reactor;independently supplying, using the processing circuit, water to eachreactor for the water phase of the reactor to reach a desired proportionof the water to the crude oil supplied to the reactor; independentlysupplying, through a dedicated oil field chemical inlet of each reactor,an oil field chemical to the reactor; and independently sampling,through a dedicated water sample outlet of each reactor, the water phaseof the reactor.

In an embodiment, the oil field chemical includes at least one of acorrosion inhibitor and a biocide.

In an embodiment, independently supplying the oil field chemicalincludes supplying the corrosion inhibitor to one of reactors andsupplying the biocide to another one of the reactors.

In an embodiment, independently supplying the oil field chemical furtherincludes supplying both the corrosion inhibitor and the biocide to yetanother one of the reactors.

In an embodiment, the method further includes removing and replacing acorrosion coupon at a bottom of the agitated water phase of each reactorduring a simulation in the reactor.

In an embodiment, each reactor further includes a bucket and theagitator of each reactor includes a rotor at the bottom of the bucket,the agitation rate being a rotation speed of the rotor, andindependently controlling the motor includes independently controllingthe motor of each reactor to adjust a height of the rotor above thebottom of the bucket of the reactor.

Any combinations of the various embodiments and implementationsdisclosed herein can be used. These and other aspects and features canbe appreciated from the following description of certain embodimentsalong with the accompanying drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of an example three-reactor apparatus tosimulate biocide performance in crude pipeline conditions, according toan embodiment.

FIG. 2 is a schematic diagram of an example liquid and gas flow for anapparatus to simulate biocide performance in crude pipeline conditions,according to an embodiment.

FIG. 3 is a cutaway view of an example reactor to simulate biocideperformance in crude pipeline conditions, according to an embodiment.

FIGS. 4A-4B are cutaway views of a reactor, such as the reactor of FIG.3 , illustrating an example coupon holder and ball valve before andafter retrieval of a corrosion coupon from the bottom of the reactor,according to an embodiment.

FIG. 5 is a schematic diagram of an example apparatus to simulatebiocide performance in crude pipeline conditions, according to anotherembodiment.

FIGS. 6A-6B are cutaway views of an example reactor to simulate biocideperformance in crude pipeline conditions, according to anotherembodiment.

FIG. 7 is a schematic diagram of an example apparatus to simulatebiocide performance in crude pipeline conditions, according to anotherembodiment.

FIG. 8 is a flow chart of an example method to simulate and evaluatebiocide performance in crude pipeline conditions, according to anembodiment.

It is noted that the drawings are illustrative and not necessarily toscale.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THE DISCLOSURE

Example embodiments of the present disclosure are directed to anapparatus to simulate crude pipeline conditions, evaluate biocideperformance in such conditions, and improve or optimize biocidetreatment strategy for such conditions. In an embodiment, a laboratorybiocontrol simulator apparatus is provided. The apparatus is designed tosimulate a two-phase crude oil pipeline (including layered oil and waterfluid phases) and evaluate biocide performance against microbialcorrosion (such as from harmful biofilms) in such a pipeline. To thisend, the apparatus simulates biofilm growth on the interior surface ofthe pipeline and provides for biocide treatment of such growth. Theapparatus is further to improve or optimize biocide treatment strategiesagainst biofilm and other microbial corrosion in such a crude oilpipeline under various water cuts (or water concentrations in the crudeoil) and flow conditions. The apparatus is further to assess microbialcorrosion due to microbial activities in the biofilm.

Microbial corrosion in crude pipelines can be addressed in a variety ofways, such as proper pipeline design, physical mitigation, and chemicalmitigation. Ideally, a pipeline should be designed to maintain aturbulent flow regime, such as maintaining the flow rates above thecritical entrainment velocity. The pipeline should also avoid deadlegs(isolated sections of the pipeline that do not usually carry a flow).Further, the pipeline should be designed to prevent the settling ofwater droplets and solid particles at the bottom of the pipe (e.g., 6o'clock position). Further, the pipeline should be scraped periodicallyto disrupt and remove any solids and water from the pipe surface. Inaddition, after scraping, corrosion inhibitors or biocides can beapplied to treat the pipe surface and control microbial activities.Nevertheless, the water cut (e.g., proportion of water) of crude oilincreases over time and the processed crude sometimes does not meet the“basic sediment and water” (BS&W) limit. In addition, crude pipelinesare often overdesigned (e.g., having excess capacity), resulting in lowaverage flow velocity, which leads to increased water and solidsdropout.

While scraping is a common practice to mitigate the crude pipelinecorrosion, some pipelines are not accessible to scraping pigs due todesign restrictions. In addition, while biocides offer possiblemitigation to microbial corrosion (such as from biofilms) in crude oilpipelines, evaluating biocide performance and optimizing the biocidetreatment strategies under crude pipeline conditions can be challenging.This is due to factors such as the impracticality of testing biocidetreatment on actual crude oil pipelines (e.g., field tests) and thedifficulty of adequately simulating crude pipeline environments on amuch smaller (e.g., laboratory) scale. For example, microbial corrosionin crude oil pipelines varies significantly depending on factors such asenvironment, type of crude oil, water content in the crude oil (watercut), flow rates, to name a few. Thus, it can be difficult to evaluatebiocide performance and optimize biocide treatment strategies for crudeoil pipelines with various water cuts and flow conditions.

Accordingly, in an example embodiment, an apparatus to simulate biocideperformance in crude pipeline conditions is provided. The apparatuscontains three parallel reactors with associated liquid and gas flowsystems and electronics, allowing concurrent or simultaneous testing ofdifferent biocide application schemes under anoxic conditions. Eachreactor includes an agitator (such as a disc rotor), six corrosioncoupon holders, an inlet for oil, water, biocide, and nitrogen (N₂) gasflow, an outlet at the bottom for water sampling, a height-adjustabledip tube as waste outlet and for oil/water mixed phase sampling,temperature and pressure sensors, a heating band, and a float contactand pressure release valve. The associated systems include liquid andgas containers, pumps, motors, various tubes for liquid and gas flows,biocide addition ports, and sampling points, sufficient to simulate thesame or nearly identical crude oil pipeline conditions in all threereactors concurrently (such as simultaneously). The electronics includetemperature regulators, frequency inverters, emergency breakers, andcomputers and software for process control and data acquisition.

The three reactors share enough components (e.g., crude oil and watersources and plumbing) to recreate nearly the same conditions in eachreactor. This allows for simultaneously testing the same environmentalconditions with as few variations as desired. This also allows for acontrol reactor to concurrently test for cause and effect relationships.This further allows for multiple identical environments to test forrepeatability. In an embodiment, each reactor system has independentcontrol of the oil and water exchange rate as well as the shear rate atthe corrosion coupon surface (e.g., bottom of the reactor). Each reactorsystem also has independent biocide treatment and independent samplingof the water phase (6 o'clock position), the oil/water interface, andthe corrosion coupons. The corrosion coupons are small metallic samples(e.g., metal plates or discs) that simulate or resemble a targetsurface, such as a pipeline wall, for which corrosion information isdesired. The coupons can be removed easily and inspected to see ifcorrosion (or corrosion precursors) are present. Each reactor systemfurther has independent control of the reactor temperature.

In addition to or in place of biocides, in some embodiments, differenttypes of oil field chemicals are concurrently (e.g., simultaneously)tested in the different reactors of the simulation apparatus. Forexample, in a three-reactor apparatus, a first reactor can be treatedwith a corrosion inhibitor only, a second reactor can be treated with abiocide only, and a third reactor can be treated with the corrosioninhibitor, followed by the biocide. With this setup, the corrosioninhibitor performance can be evaluated, as can that of the biocide, ascan that of the combined treatment, all under otherwise nearly identicalconditions.

In an embodiment, the simulation of the pipeline water cut and fluidexchange rate uses two peristaltic pumps delivering oil and water,respectively, at various ratios. In addition, the shear rate in thepipeline is simulated in each reactor by adjusting the rotation speedand the height of the rotor. The apparatus also includes sensors fortemperature and pressure monitoring of each reactor. The apparatus, ormore specifically each of the reactors, operates autonomously underanoxic conditions while the microorganisms grow in the water phase andcolonize the coupon surface. As such, the apparatus requires minimalmanual labor, such as only during setup, sampling, exchange of supplyfluids, and when de-commissioning an experiment. In an embodiment, theapparatus is cleaned with chemical flushing and sterilized with anin-place autoclave using wet heat.

While much of the present disclosure is directed to the simulation ofbiocide performance under crude oil pipeline conditions, the presentdisclosure is not limited to such applications. In other embodiments,the effects of different oil field chemicals, such as corrosioninhibitors, scale inhibitors, or the like, are simulated in the crudeoil pipeline conditions.

In an example environment to simulate, a two-phase sweet crude pipelineis used as a model pipeline for the engineering design of an apparatusaccording to an embodiment. The model pipeline is 129 miles long, using46 inch and 48 inch pipe to transport sweet crude oil though a desertenvironment. Usually, the pipeline has low flow velocity, such as lessthan 0.9 meters per second (m/s). The pipeline is not treated withcorrosion inhibitors or biocides. The pipeline has experienced severeinternal corrosion due to microbial effects, and has needed extensiverepairs. By compiling the pipeline's operating conditions andparameters, the major characteristics of the pipeline can be summarizedas: a two-phase system (sweet crude oil and water), with aphase-separated liquid flow, water being at the 6 o'clock (low)position, as well as the corrosion. By using an apparatus according toan embodiment disclosed herein to simulate such a pipeline on a muchsmaller scale, effective biocide treatment plans can be identified andtested without the inconvenience and cost of using the actual pipelineto conduct such an investigation.

In an embodiment, an apparatus to simulate various crude pipelineconditions with concerns of microbial corrosion is provided to identifypipelines that would benefit from biocide treatment for microbialcontrol. The microbial corrosion in a sweet crude oil pipeline is oftencaused by water and solids that drop out and accumulate at low spots dueto flow conditions such as low flow velocity or stagnant flow. Theapparatus provides for simulation of separated oil and water phases,turbulent mixing of oil and water phases, simulation of pipeline shearrates (e.g., pipeline flow velocity changes across different parts ofthe interior of the pipeline), simulation of water at the 6 o'clockposition, and control of the water cut and temperature. The apparatusalso provides for up to six commercially available corrosion coupons(e.g., flat discs) in each reactor, coupon removal and replacementduring experiments, biofilm growth and biocide treatment, data transferto computers and storage devices (such as an Excel spreadsheet), andsafety features.

In an embodiment, computational fluid dynamics (CFD) simulation and flowcalculations are used to evaluate the fluid flow in a model pipeline. Byusing a range of water cuts and flow velocities in CFD simulations, thedominant flow type under various flow conditions can be determined. Byway of example, dimensionless numbers (such as Reynolds, Froude, andWeber numbers) can be used to understand fluid dynamics when scalingdown from a pipeline to a laboratory apparatus such as an embodiment.Using conventional equations, the surface shear rate can be calculatedto simulate the flow velocity in the pipeline below which biofilmdevelopment significantly increases on the surface of the pipeline wallor on the corrosion coupons. CFD simulation and flow calculations canalso be used to determine the most important simulation parameters forthe apparatus.

The design of the test cell or reactor can factor in these simulationpriorities, including: phase separation (e.g., the liquid composition atthe coupon surface in the apparatus should match that of the 6 o'clockpipeline position), shear rate at the coupon surface (e.g., should matchthe 6 o'clock pipeline position, focusing on low flow velocity such asfrom 0.3 m/s to 1.0 m/s), turbulence magnitude (turbulence (Reynoldsnumber) should match that of the pipeline to maintain interphase mixing,growth potential of cells, and efficacy of biocides), and water cut(lower priority, with CFD simulation showing a phase separation underall relevant pipeline conditions, such as water cut above 3.3% and flowvelocity below 1.5 m/s).

In accordance with various embodiments, an apparatus to simulate biocideperformance in crude pipeline conditions is provided. The apparatus isconfigured to simulate two-phase crude pipeline conditions by:simulating separated oil and water phases, simulating flow velocity inthe crude pipeline via shear rate simulation, simulating turbulent flowin the crude pipeline, controlling the oil and water ratio, simulatingwater deposits at the 6 o'clock position, simulating corrosion at the 6o'clock position, and simulating crude oil pipeline temperatures. Theapparatus is further configured to simulate biofilm growth on pipelinesurfaces by: allowing biofilm formation and growth on the surface ofcorrosion coupons at the 6 o'clock position, allowing biofilm formationand growth under anoxic conditions, simulating phase exchange at theoil/water interphase (that provides nutrition for biofilm growth), andsimulating the impact of flow velocity and shear rate on biofilm growth.

In addition, the apparatus is configured to evaluate biocide performanceand optimize treatment schemes under crude pipeline conditions by: usingthree parallel reactors for simultaneous testing of different biocideapplication schemes and treatment optimization; providing biocidetreatment to each reactor; providing coupon removal and replacementduring experiments; providing sampling of the water, the oil/waterinterphase, and the corrosion coupons during the experiments; andproviding microbial corrosion assessment on the metal coupons.

In an embodiment, a laboratory apparatus is configured to simulatetwo-phase sweet crude pipeline conditions, develop biofilm on metalcoupon surfaces, evaluate biocide performance on such biofilmdevelopment, and optimize treatment schemes under the simulated pipelineconditions. Such an apparatus, operating under the simulated crude oilpipeline conditions, improves the biocide evaluation accuracy overwater-based systems, shortens field trial durations, acceleratesoptimization of treatment programs for crude pipelines, and saves thecost of biocide field trials.

Laboratory validation of such an apparatus includes microbialenrichment, validation of biofilm growth, and evaluation of biocideperformance. Microbial enrichment includes collecting crude oil andwater samples from a model or target pipeline, and formulating anartificial growth media based on the geochemical composition of themodel pipeline water, to promote growth of the major corrosion-relatedbacteria, such as sulfate-reducing bacteria (SRB) and acid-producingbacteria (APB). The microbial enrichment further includes analyzing themodel pipeline water and the enrichment culture from this water todetermine the number of various microorganisms and the microbialcommunity compositions, to make sure the basic microbial compositionsare similar.

In an embodiment, a reactor to simulate biocide performance in crudepipeline conditions is provided. The reactor includes six corrosioncoupons and a rotor to generate the required shear to simulate thedesired pipeline conditions. Water and crude oil enter the reactor viaan inlet, with the water cut being controllable by individual pumps thatdeliver the fluids. An immersion tube provides an outlet from thereactor. The immersion tube is height adjustable within the reactor tosample, for example, oil, water, or the mixed phase oil and water at theboundary between the two phases. Each coupon is secured with acorresponding coupon holder that uses a ball valve to deploy, retrieve,or exchange coupons during an experiment in the reactor. The rotor speedis controlled by a corresponding shaft and bearings below and outsidethe reactor.

FIG. 1 is an illustration of an example three-reactor apparatus 100 tosimulate biocide performance in crude pipeline conditions, according toan embodiment. Structurally, the apparatus 100 includes an aluminumframe 110 to support the reactors 130 and their corresponding agitatormotors 135, and a transparent plastic enclosure 120 (such as plexiglass)to safeguard and isolate the reactors 130 and other equipment (such asfor gas containment) while permitting visual observation. The apparatus100 further includes the three reactors 130 and their correspondingmotors 135 (e.g., 3 phase, 380 volt (V) motors). Each reactor 130includes six corrosion coupons 140 for observing corrosion activity(such as microbial corrosion) together with a rotor for simulatingpipeline fluid flow and sensors for determining, for example,temperature and pressure within the reactor 130.

The apparatus 100 further includes various pumps 150 (such asperistaltic pumps) and tubing (such as stainless steel (SS) andflexible) for pumping and delivering liquids and gases such as water,crude oil, N₂, and liquid and gas samples and wastes. The apparatus 100also includes tanks 160 for holding the different liquids used (e.g.,input or output) by the reactors, such as water, oil, and waste liquid.In addition, the apparatus 100 includes various electronic equipment170, such as an electronic panel for displaying simulation data,computers for electronically processing the data, and software forconfiguring the computers to process the data and make the apparatus 100function as designed. The electronics can include, for example, one ormore custom hardware circuits, programmable logic circuits (PLCs), orcomputer processors configured with code or other logic to carry out thetasks assigned to the circuits or processors. The electronics can alsoinclude a user interface equipped with a touch screen to permit computerinteraction.

In further detail, the apparatus 100 includes three parallel reactors130 (e.g., 12 liters (L) apiece) mounted on an aluminum frame 110 with aplexiglass enclosure 120. An explosive gas sensor and a hydrogen sulfide(H₂S) sensor are mounted at the top of the frame 110, inside theplexiglass enclosure 120, and transmit their measurements to aprogrammable logic controller (PLC, part of the electronics 170). ThePLC is configured with code or other programmable logic that causes thePLC to carry out the tasks assigned to it, such as alerting an operatorto unsafe or undesired levels of explosive gas or H₂S detected. Eachreactor 130 includes a disc rotor, six corrosion coupon holders, aninlet for oil, water, biocide, and N₂ gas, an outlet at the bottom forwater sampling, a height-adjustable dip tube for use as a waste outletand for oil/water mixed phase sampling, temperature and pressuresensors, a heating band 140, and a float contact and pressure releasevalve. The reactor 130 can be cleaned, for example, with a manualchemical scrub, and sterilized by an in-place autoclave with wet heat.

The disc rotor is made of 316 stainless steel (SS), with 300 millimeter(mm) diameter and 8 mm thickness. The disc rotor is electricallyinsulated from the reactor 130 by a collar made ofpolytetrafluoroethylene (PTFE, commonly known as Teflon). It is poweredby a gear motor 135 with rotation speeds of between 20 and 220revolutions per minute (RPM or rpm). The motor 135 is controlled usingthe PLC through a frequency inverter. The height of the disc rotor canbe adjusted between 5 mm and 10 mm above the coupons (e.g., 5-10 mmabove the bottom of the reactor 130) using the motor 135. The shear rateat the coupon surface is controlled by the rotation speed and the heightof the rotor. In addition, each reactor 130 can hold six commercialdisc-shaped corrosion coupons with exposed surface area of 1.12 squareinches (7.2 square centimeters, or cm²). Each corrosion coupon is madefrom mild steel (e.g., alloy C1018, from Alabama Specialty Products) andmounted in a polyether-ether-ketone (PEEK) coupon holder for isolationfrom the metal surface of the reactor base. Each coupon can be removedand replaced during an experimental run and with minimal disruption toany experiment in progress.

The electronics panel, computer, and software 170 (collectively known as“electronics 170) includes the PLC configured with code (or otherprogrammable logic) to carry out process control and data acquisition.The PLC is further configured (e.g., with code or other programmablelogic) to frequently (such as continuously) read data from thetemperature regulators, the pressure sensors, and the gas sensors. ThePLC is also configured to control the pumps and the frequency inverters.The electronics 170 can also include a computing device (such as alaptop, a workstation, a tablet, a smartphone, part of a server, or adedicated hardware circuit, as in an FPGA or ASIC, or the like). Theinstrumentation data obtained by the apparatus 100 can be stored orrecorded in a non-transitory storage device, such as a disk drive orsolid state storage device, such as a network-accessible storage deviceattached to a wired or wireless network. The electronics 170 furtherincludes one or more temperature regulators each configured to read thereactor temperature through the temperature sensors and adjust thetemperature through the heating bands 140. The electronics 170 alsoincludes one or more frequency inverters each configured to set therotation speed of the motors 135, allowing the motors 135 to run between20 rpm and 220 rpm.

In addition, the electronics 170 includes an emergency breaker that isconfigured to work with an emergency button to stop all hazardous partsin case of an emergency. For example, in an embodiment, the emergencybreaker, once engaged (such as by pushing the emergency button), isconfigured to force the motors, pumps, and heating for the apparatus 100to stop. The electronics 170 further includes a computer configured bycode to perform as the primary user interface, connected to the PLC viaan Ethernet cable. By way of example, the computer can be configured bycode to run a LabVIEW software application customized for the apparatus100. The LabVIEW customization can include code that configures thecomputer to control various parameters frequently (such as continuously)when running the apparatus 100, such as the oil and water mix ratio, theshear rate, and the reactor temperature. The customization can furtherinclude code to provide step-by-step guides for manual handling andmaintenance of the apparatus 100, such as liquid container changes,biocide addition, sample collection, cleaning, and sterilization.

The software can include further instructions that when executed by thecomputer, cause the computer to control parameters such as rotationspeed of the rotor, test cell temperature, and fluid exchange rate. Thesoftware can also configure the computer to assist users with when andhow to perform maintenance (e.g., tank changes, removal and insertion ofcoupons, extraction of water samples, addition of biocide, and thelike). By way of example, the software can configure the computer toreceive input from and direct output to a touch screen configured tooperate as a control center for the apparatus 100.

The customization can also include code that configures the computer toperform data logging and output: By way of example, the software caninclude code that configures the computer to log relevant informationabout an experimental run (e.g., rotor rotation speed, reactortemperature, reactor pressure, oil/water liquid flow rates, remainingliquid volume; date, time, and type of manual operations; and results ofsample analyses), to save data in transition-minimized differentialsignaling (TDMS) format, and to export data to an electronic spreadsheet(such as an Excel workbook). In addition, the customization canconfigure the computer to calculate the shear rate based on pipelineconditions, and to determine a rotor rotation speed to match thepipeline shear rate.

FIG. 2 is a schematic diagram of an example liquid and gas flow for anapparatus 200 to simulate biocide performance in crude pipelineconditions, according to an embodiment. The apparatus 200 includes threereactors (including reactor 260) for simulating the crude oil pipeline.Each reactor 260 includes a rotor 258 for simulating the crude pipelineflow conditions in the reactor 260. The rotor 258 is driven by a shaft256 connected to a motor for controlling the rotation speed of therotor. The apparatus 200 also includes both SS tubes (e.g., ¼ inch SStube) and flexible tubing to route the various fluids (liquids andgases) between the different components throughout. The liquidcontainers include an oil tank 204, a water tank 214, and a waste tank294 (for example, Thielmann SS pressure vessels can be used for thesetanks). Each such tank is also equipped with a built-in pressure reliefvalve and a gas inlet for pressure equalization. Within the reactor 260,liquid can be drawn from the bottom of a height-adjustable dip tube 268(e.g., to obtain a sample of an oil/water mixture at the boundary of theoil and water phases in the reactor 260).

Two peristaltic pumps (such as with three channels each, one channel foreach reactor 260), including oil pump 208 and water pump 218, deliveroil and water at various ratios to the three reactors (e.g., using oilvalve 210, water valve 220, and mixing valve 230, for eventual deliveryto an inlet valve 250 and reactor 260 via mixing valve 240). The inletvalve 250 also serves as a bypass valve to divert any inputs from thereactor 260. Check valves, such as check valve 206 between the oil tank204 and oil pump 208, check valve 216 between the water tank 214 andwater pump 218, and check valve 236 between the mixing valve 230 andmixing valve 240, can be used to prevent unintended backflow along theliquid paths. The pump rate at each pump can be adjusted, for example,between 0.013 milliliters per minute (ml/min) and 12.7 ml/min for 1.52mm tubing. Various tubing materials can be used in the apparatus 200,such as SS, PTFE, and Viton tubes. SS tubing can be mainly for liquidflow, PTFE for gas flow, and Viton for the flexible connections of themain system, as one example of implementing a particular embodiment. Thetubes can be cleaned and sterilized, for example, by chemical flushing.

N₂ gas flow is used for a variety of purposes, such as providing anoxicconditions for the simulation. N₂ gas flows 202 and 212 to the oil tank204 and water tank 214, respectively, equalize pressure in the tankswhile providing anoxic conditions. Further, N₂ gas flow 232 is providedto the inlet valve 250 (via mixing valve 240) to help drain the reactor260 during cleaning and maintenance. In addition, N₂ gas flows aresupplied to corresponding coupon holder ball valves 252 and 254 of thereactor 260 to prevent an air ingress to the reactor 260 and limit thespill of fluid during coupon insertion, removal, and replacement. Thecoupons are at the top of the coupon holders 252 and 254, flush with thebottom inside surface of the reactor and below the rotor 258, andremovable/replaceable via the corresponding ball valves with minimaldisruption of the experiment in the reactor 260.

Biocide can be added to the mixed phase liquid at the mixing valve 240(via biocide inlet 234) immediately before the mixture enters thereactor 260. For example, the biocide inlet 234 can be a syringe with aLuer-lock (or Luer taper) connection. The check valve 236 (one-wayvalve) ensures that the biocide only flows towards the reactor 260, notbackwards toward the liquid supplies. The biocide (or other oil fieldchemical, such as corrosion inhibitor or scale inhibitor) can bedelivered independently and distinctly for each reactor 260 (e.g., viadedicated biocide inlets 234). The reactor 260 further includes a floatcontact 262 and pressure release valve 266 for releasing excess pressurein the reactor 260. The output of the float valve 266 is directed to amixing valve 270 that also receives the output of the dip tube 268.

In addition, the reactor 260 includes a temperature sensor 276 and apressure sensor 278 that measure (such as periodically) the temperatureand pressure of the inside of the reactor 260. This can help ensure thatthe desired environmental conditions (or ranges) for the simulation aremaintained throughout the experiment. For example, the temperaturesensor 276 can mount to a lid of the reactor 260 to monitor thetemperature of the reactor 260 while the pressure sensor 278 can mountto the top of the dip tube 268 to monitor the pressure of the reactor260 from the mixing valve 270.

The reactor 260 includes a water port 264 for sampling the water phase(bottom, corresponding to the 6 o'clock position of the pipeline beingsimulated) of the reactor 260. The water port 264 combines with anoutput of the mixing valve 270 at an outlet valve 274. The output of theoutlet valve 274 combines with the output of the bypass valve 250 (forfluid diverted from entering the reactor 260). After the outlet lines ofthe reactor 260 have combined to one at the mixing valve 280, there is aliquid sampling point 284. The sample point 284 allows the operator orautomated collection (e.g., under control of a processor configured bycode to manage the collection) to collect samples from the reactor 260.For instance, the samples can come from the water phase (from the bottomof the reactor 260) or the oil/water mixed phase (from theheight-adjustable dip tube 268 inside the reactor 260).

The mixing valve 280 can further divert output fluid from the reactor260 to the waste tank 294 via a waste valve 290. A check valve 286 isused to prevent backflow from the waste tank 294 to the mixing valve 280(and other components, such as the reactor 260 or sample point 284). Asafety valve 292 can act as a fail-safe should preset or predeterminedpressure or temperature levels of the waste fluids be exceeded. Anexhaust vent 296 is provided to remove any (excess) gas entering thewaste tank 294.

FIG. 3 is a cutaway view of an example reactor 360 to simulate biocideperformance in crude pipeline conditions, according to an embodiment.The reactor 360 includes a bucket 361 with a lid 373 to contain thetwo-phase oil and water combination that simulates the crude pipeline.The reactor 360 further includes six coupons (such as corrosion coupons363 and 365) at the bottom of the bucket 361 secured by correspondingcoupon holders (such as coupon holders 353 and 355, respectively). Eachcoupon holder 353 or 355 in FIG. 3 is designated with two lines, one fora lower portion of the coupon holder and one for an upper portion of thecoupon holder. The coupon holders 353 and 355 allow for retrieval of therespective coupons 363 and 365 during an experiment using correspondingball valves 352 and 354, as illustrated in more detail in FIGS. 4A-4B.To this end, corresponding N₂ gas flows are supplied to the ball valves352 and 354 to, for example, prevent air ingress to the reactor 360 andlimit spills during removal and replacement of the coupons 363 and 365using the ball valves 352 and 354, respectively.

The reactor 360 further includes a rotor 358 connected to a shaft 356that is connected to bearings 357 (e.g., to stabilize and improveperformance of the shaft 356) and a motor for rotating the rotor 358using the shaft 356 and the bearings 357. The rotor 358 simulates thepipeline flow conditions in the bucket 361. The rotor 358 is at thebottom of the bucket 361, above the coupons 363 and 365. The reactor 360further includes a dip tube 368 for sampling the oil and water at thephase boundary between the two phases. In addition, the reactor 360includes a float contact 362 coupled to a float valve 366 at the top ofthe reactor 360. The float contact 362 includes a hollow SS ball thatfloats on the interface between oil and gas (at the top of the reactor360). The float contact 362 is mounted at the top of the lid 373. Whenthe gas amount in the reactor 360 increases, the ball lowers, and thefloat valve 366 opens to reduce the gas headspace in the reactor 360.The reactor 360 further includes a temperature sensor 376 mounted to thelid 373 to monitor the temperature inside the reactor 360.

FIGS. 4A-4B are cutaway views of a reactor, such as the reactor 360 ofFIG. 3 , illustrating an example coupon holder 453 and ball valve 452before and after retrieval of a corrosion coupon 463 from the bottom ofthe reactor, according to an embodiment. Many of the components of thereactor of FIGS. 4A-4B are similar to the reactor 360 of FIG. 3 , suchas rotor 458, bearings 457, and steel axle (shaft) 456. FIG. 4Aillustrates the corrosion coupon 463 flush mounted to the bottom of thereactor. The coupon 463 is at the top of and secured to the couponholder 453 (such as by a center-mount screw). The coupon holder 453 islong, extending through the ball valve 452 (in the open position, asindicated by the parallel orientation of the ball valve handle 451 withrespect to the coupon holder 453), and includes O-rings below the coupon463 to form a watertight seal with the reactor.

FIG. 4B, on the other hand, illustrates the corrosion coupon 463 afterretrieval from the reactor, with the ball valve 452 in the closedposition, as indicated by the perpendicular orientation of the ballvalve handle 451 with respect to the coupon holder 453. The closed ballvalve 452 seals the reactor, permitting complete removal of the couponholder 453 and access to the coupon 463 with minimal liquid loss fromthe reactor in the process. N₂ gas is further directed to the ball valve452 to minimize the risk of air (oxygen) ingress to the reactor duringthe coupon removal and replacement process. The coupon 463 can beanalyzed for corrosion-related effects such as biofilm presence, weightloss, pitting, or other metallurgical phenomena indicative of corrosion.Further, a replacement coupon 463 can be flush mounted to the bottom ofthe reactor by attaching the replacement coupon 463 to the coupon holder453 (e.g., with a center-mount screw) and reversing the retrievalprocess.

FIG. 5 is a schematic diagram of an example apparatus 500 to simulatebiocide performance in crude pipeline conditions, according to anotherembodiment. The apparatus 500 includes three main parts: liquid and gasflow (including containers, piping, and pumps), test cells/reactors(including coupon holders, fluid injection ports, and sampling points),and electronics (including computer and software). The software containscomputer instructions that when executed on the computer, cause thecomputer to control the apparatus 500 and acquire data from differentinstrumentation devices of the apparatus 500. In an embodiment, theapparatus 500 includes three parallel test cells for simultaneoustesting of multiple biocide treatments. However, the present inventionis not limited thereto, and in other embodiments, different numbers ofparallel test cells are present, such as four or two.

In further detail, the apparatus 500 includes storage containers 504,514, and 594 for crude oil, water, and waste liquid, respectively, tomanage the liquid input and output for the apparatus 500. The apparatus500 further includes oil pump 508 and water pump 518 (such asperistaltic pumps) to deliver the crude oil and water from the oil andwater containers 504 and 514, respectively, to the reactors. Theapparatus 500 also includes biocide injection ports 534 for supplyingbiocide (or other oil field chemical, such as a corrosion inhibitor orscale inhibitor) to the corresponding reactors.

Considering only a single reactor for ease of description, the apparatusfurther includes a test cell (or reactor) 560 for simulating thetwo-phase crude pipeline. The test cell 560 includes corrosion coupons563 for testing the water phase (e.g., the lower or water portion) ofthe test cell 560 for symptoms indicative of pipeline corrosion (e.g.,microbial corrosion such as biofilm-induced corrosion). The test cell560 further includes a fluid sample retrieval port 564 for sampling thewater phase of the liquid in the test cell 560, such as to test forbiofilm, conditions that serve as precursors to biofilm, effects ofbiocide treatment, or to test for similarity of the water phase in thetest cell 560 versus that of the crude pipeline being simulated. Theapparatus 500 also includes a waste valve 590 for eliminating wastefluids (e.g., undesired, unnecessary, or excess liquids or gases) fromthe test cell 560 to the waste container 594.

In an embodiment, each of the test cells 560 has the followingcapabilities: oil/water separation (e.g., two-phase liquid portion, withwater at the 6 o'clock position and oil at the 12 o'clock position),control of the shear rate (e.g., the velocity gradient as measuredacross the diameter of the fluid-flow channel, or in this case, withinthe test cell 560), control of the mixing of oil and water at theinterphase of the two-phase system, and control of the water cut (e.g.,ratio of water to oil or of water to the total liquid).

FIGS. 6A-6B are cutaway views (side and bottom, respectively) of anexample reactor to simulate biocide performance in crude pipelineconditions, according to another embodiment. There are many possibledesigns of such reactors and their corresponding agitators. However, thedesign in FIGS. 6A-6B (including a closed bucket with a disc rotor andbottom corrosion coupons) is used throughout as an example reactordesign that has overall characteristics that compare favorably to othersimilar or comparable designs. These characteristics include good phaseseparation of the oil and water, good control of the shear rate at thecoupons, good control of oil and water interaction at the interphase,and good cleaning and sterilization properties. In addition, the examplereactor design has other desirable qualities, such as a manageableamount of liquid to simulate the crude pipeline (e.g., using the closedbucket as opposed to a more pipeline-like design such as a closed flowloop) as well as the ability to use standard commercial corrosioncoupons (instead of custom-shaped coupons).

In further detail, the reactor design of FIGS. 6A-6B includes a bucket661 closed with a lid 673 to produce a sealed system having a few accessports as described throughout. The bucket 661 holds a sample of crudeoil 665 and water 667 sufficient to simulate the conditions of a crudepipeline whose corrosion (such as microbial corrosion) treatment isbeing investigated. In addition, the reactor design includes a rotor 658near the bottom of the bucket 661 that rotates (as controlled by a shaft656 coupled to a motor). The rotor rotation rate can be varied, such asbetween 20 rpm and 220 rpm, to better simulate the flow conditionswithin the crude pipeline. The rotor height can also be adjusted (suchas within the water phase) to better simulate desired crude pipelineconditions.

The flow velocity is modeled using a CFD simulation and illustratedschematically in FIG. 6B, where the direction, size, and transparency ofthe arrows 669 indicates the direction and speed of the correspondingflow at that location. The larger, darker arrows near the perimeterindicate a relatively strong (clockwise) flow of water, as opposed tothe smaller, fainter arrows closer to the center, which indicate arelatively weak (but still clockwise) flow of water. Accordingly, duringthe simulation, the water at the sides of the bucket 661 reaches ahigher height compared to that at the center of the bucket 661.

Also illustrated in FIGS. 6A-6B are six corrosion coupons 663 flush withthe bottom of the inside of the bucket 661. The coupons 663 areconfigured to be deployable and removable during a simulation withlittle or minimal impact to the simulation (such as through couponholders illustrated and discussed elsewhere). Since the extent and therate of corrosive activity is relatively slow and tracked over time, sixcoupons 663 provides a sufficient number of sample points to getreliable data over time, permitting testing of one or two points at atime while other regions continue to be subjected to the simulation.

In the reactor design of FIGS. 6A-6B, the shear rate at the couponsurface (e.g., bottom of the bucket 661) can be adjusted using therotation speed and height of the disc rotor 658. The horizontal discrotor 658 facilitates phase separation and oil/water mixing. Sixcommercially available, flat disc coupons 663 are flush mounted at thebottom of the test cell.

FIG. 7 is a schematic diagram of an example apparatus 700 to simulatebiocide performance in crude pipeline conditions, according to anotherembodiment. The apparatus design of FIG. 7 has some features worthnoting. The apparatus 700 uses a bucket test cell/reactor having a discrotor 758 (driven by a shaft 756) and bottom coupons 763. The apparatus700 further uses several such test cells, such as three. For example,three nearly identical reactors sharing as many common components aspossible provides for simultaneous testing of different biocideapplication schemes under close to identical conditions. It should benoted that using fewer such test cells makes such simultaneous testinglimited or impossible, while using more than three complicates thedesign of the apparatus 700 while only providing marginal addedsimultaneous testing capability. Nonetheless, in other embodiments,different numbers of test cells, such as four, five, or even two areprovided.

In FIG. 7 , a single reactor is illustrated. Through the use ofelectronics, such as a computer programmed with code to carry out itsfunctions, the user can control simulation parameters such as the oiland water flow rate (e.g., through oil supply flow 704 and water supplyflow 714), the rotation speed of the rotor 758 (corresponding to thepipeline flow velocity), and the fluid composition (water cut orproportion of water 767 to oil 765) in the reactors. Nitrogen (N₂) flow732 is used to ensure anoxic conditions in the system. A sample point784 is located downstream of the reactor for sampling and analysis ofthe water phase (e.g., from a bottom port) or the oil/water mixed phase768 (e.g., from a dip tube adjusted to the height of the interphase ofthe oil 765 and water 767). Undesired gas 766 is vented from the testcell. Undesired fluids are directed to a waste flow 794 (e.g., foreventual collection and disposal).

The apparatus 700 has some key features: three experiments can beconducted in parallel using nearly identical configurations (except forvariables being tested), the oil and water exchange rate can becontrolled separately for each reactor (such as by using twocorresponding peristaltic pumps for the oil and water, respectively),and the oil and water phases in the test cell stay separated (as theyare in a crude pipeline being simulated). Further features include: theability to simulate turbulent mixing of the oil and water phases, theability to control the shear rate at the coupon surface separately foreach reactor (such as by the rotation speed and height of the rotor),the ability to allow biofilm development on the coupon surface and todirect biocide treatments to these surfaces, the ability to add biocideseparately to each reactor using syringes with Luer-lock connections,and the ability to sample liquid phases separately for each reactor(e.g., through a fixed water sampling port and an adjustable dip tubefor oil/water interface sampling).

Still further features include: the ability to install and replacecorrosion coupons during experiments with minimal disruption to anongoing experiment, the ability to maintain a sterilized setup (e.g., bychemical flushing and an in-place autoclave), the ability to operateunder anoxic conditions (e.g., by N₂ flushing), and the ability tocontrol reactor temperature (e.g., by using a heating band together witha temperature regulator).

FIG. 8 is a flow chart of an example method 800 to simulate and evaluatebiocide performance in crude pipeline conditions, according to anembodiment. Portions of this and other methods disclosed herein can beperformed on a custom or preprogrammed logic device, circuit, orprocessor, such as the PLC, computer, software, and other electronics170 of FIG. 1 . The device, circuit, or processor can be, for example, adedicated hardware device or computer server, or a portion of a serveror computer system. The device, circuit, or processor can include anon-transitory computer readable medium (CRM, such as read-only memory(ROM), flash drive, or disk drive) storing instructions that, whenexecuted on one or more processors, cause portions of the method 800 (orother disclosed method) to be carried out. It should be noted that inother embodiments, the order of the operations can be varied, and thatsome of the operations can be omitted.

In the example method 800, experiments are designed to evaluate andoptimize the biocide performance under the simulated crude pipelineconditions. The method 800 can be performed, for example, using crudepipeline simulation apparatus 200. In the method 800, processing beginswith acquiring 810 the conditions and characteristics of the crude oilpipeline of interest, such as the water cut in the transported crudeoil, the flow velocity of the crude oil in the pipeline, temperature,and the like. Of particular interest are the pipeline characteristicsthat affect the production of biofilm and other sources of microbialcorrosion.

The method 800 further includes determining 820 (such as with a PLC orcomputer processor) the rotor rotation speed of a reactor (such as rotor258 in reactor 260) in order to simulate turbulent flow and the effectof flow velocity on the pipeline inner surface. The rotor rotation speedcan be calculated, for example, using a flow calculator applicationincorporated in a LabVIEW software application customized by code tocalculate the corresponding rotor rotation speed from the desired flowvelocity. The flow velocity on the pipeline inner surface furtheraffects the biofilm formation and growth, which are key indicators andprecursors to microbial corrosion. The flow velocity on the pipelineinner surface is also expressed as the shear rate on the coupon surfaceof the simulator, which equates to the 6 o'clock position of thepipeline.

The method 800 also includes delivering 830 water and crude oil to threeparallel reactors independently and at predetermined ratios and flowrates to simulate the water cut and fluid exchange rate in the pipeline.By way of example, the simulation apparatus includes two peristalticpumps (such as oil pump 208 and water pump 218), one for crude oil andone for water. Each pump has three channels, one for each reactor in thethree-reactor simulation apparatus. The two pumps are programmable todeliver the desired water and crude oil ratio and flow rates, ascontrolled by an electronic circuit such as the PLC or computerprocessor configured with code. In addition, the method 800 includesregulating 840 the temperature of the reactors to simulate the pipelineoperation temperature. This can be accomplished, for example, by the PLCactivating a heating band that heats the reactor in response to atemperature sensor indicating the reactor is below the desiredtemperature to simulate the pipeline operation.

The method 800 further includes adding 850 biocide to the mixed crudeoil/water flow independently for each reactor. By way of example, thebiocide can be added through a dedicated biocide inlet (such as biocideinlet 234) for each reactor. In this fashion, different treatmentregimens can be applied, such as different injection dosages, durations,and frequencies in order to evaluate the biocide performance or optimizethe treatment regimens. The method 800 also includes obtaining 860various samples (such as through water sampling port 264 and dip tube268) during the experiment to evaluate the effect of the biocide. Forexample, the samples can include water samples from the bottom of thereactor and mixed crude oil/water samples from the interphase region ofthe crude oil and water. The water samples can be obtained, forinstance, from a water sample port at the bottom of the reactor whilethe mixed crude oil/water samples can be obtained through aheight-adjustable dip tube. The samples can be used, for example, todetermine microbial activities and biocide residual concentration,before and after the biocide treatment.

In addition, the method 800 includes retrieving 870 one or morecorrosion coupons from the bottom of the reactor. By way of example,each reactor can include six commercially available, flat disc corrosioncoupons (such as corrosion coupon 463) that are flush mounted to thebottom of the reactor. The coupons are individually retrievable andreplaceable from the reactor during and after an experiment. The couponscan be retrieved from the reactor, for instance, for biofilm analysis,weight loss analysis, pitting analysis, and other metallurgicalanalyses. Further, new corrosion coupons can be inserted during theexperiment to replace any retrieved coupons. This can be accomplished,for example, through special design of a corrosion coupon holder (suchas corrosion holder 453) to minimize oil spill and avoid oxygen ingressduring the coupon replacement. The method 800 further includes cleaning880 the device after an experiment, using chemical flushing andsterilization with an in-place autoclave applying wet heat. This is animportant feature that should be part of any microbiology work toeliminate carry-over contamination from one experiment to the next.

The methods described herein may be performed in part or in full bysoftware or firmware in machine readable form on a tangible (e.g.,non-transitory) storage medium. For example, the software or firmwaremay be in the form of a computer program including computer program codeadapted to perform some or all of the steps of any of the methodsdescribed herein when the program is run on a computer or suitablehardware device (e.g., FPGA), and where the computer program may beembodied on a computer readable medium. Examples of tangible storagemedia include computer storage devices having computer-readable mediasuch as disks, thumb drives, flash memory, and the like, and do notinclude propagated signals. Propagated signals may be present in atangible storage media, but propagated signals by themselves are notexamples of tangible storage media. The software can be suitable forexecution on a parallel processor or a serial processor such that themethod steps may be carried out in any suitable order, orsimultaneously.

It is to be further understood that like or similar numerals in thedrawings represent like or similar elements through the several figures,and that not all components or steps described and illustrated withreference to the figures are required for all embodiments orarrangements.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a,” “an,” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

Terms of orientation are used herein merely for purposes of conventionand referencing, and are not to be construed as limiting. However, it isrecognized these terms could be used with reference to a viewer.Accordingly, no limitations are implied or to be inferred. In addition,the use of ordinal numbers (e.g., first, second, third) is fordistinction and not counting. For example, the use of “third” does notimply there is a corresponding “first” or “second.” Also, thephraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including,” “comprising,” “having,” “containing,” “involving,” andvariations thereof herein, is meant to encompass the items listedthereafter and equivalents thereof as well as additional items.

While the disclosure has described several exemplary embodiments, itwill be understood by those skilled in the art that various changes maybe made, and equivalents may be substituted for elements thereof,without departing from the spirit and scope of the invention. Inaddition, many modifications will be appreciated by those skilled in theart to adapt a particular instrument, situation, or material toembodiments of the disclosure without departing from the essential scopethereof. Therefore, it is intended that the invention not be limited tothe particular embodiments disclosed, or to the best mode contemplatedfor carrying out this invention, but that the invention will include allembodiments falling within the scope of the appended claims.

What is claimed is:
 1. An apparatus to simulate biocide performance incrude oil pipeline conditions, the apparatus comprising: an agitatormotor; a reactor to simulate a two-phase crude oil pipeline andincluding a crude oil phase above a water phase, the reactor comprisingan agitator to control a flow of the water phase in the reactor inresponse to the agitator motor that drives an agitation rate of theagitator; a crude oil inlet to supply crude oil to the reactor for thecrude oil phase; a water inlet to supply water to the reactor for thewater phase; a control circuit configured by logic or code to control aproportion of the water to the crude oil supplied to the reactor by thecrude oil inlet and the water inlet, and control the agitator motor todrive a desired agitation rate of the agitator; a biocide inlet tosupply biocide to the reactor; a water sample outlet to sample the waterphase of the reactor; a plurality of coupon holders each configured tohold a corrosion coupon at a bottom of the agitated water phase of thereactor during the simulation of the two-phase crude oil pipeline, andpermit removing and replacing of the held corrosion coupon during thesimulation; a ball valve for each coupon holder, the ball valve beingconfigured to seal the reactor during the removal and replacement of thecorrosion coupon; and a height-adjustable dip tube to obtain a mixedsample of the crude oil phase and the water phase of the reactor at aninterphase region of the crude oil phase and the water phase in thereactor.
 2. The apparatus of claim 1, wherein the reactor furthercomprises a plurality of reactors each having a dedicated biocide inletand a dedicated water sample outlet, and the control circuit is furtherconfigured by logic or code to independently control the proportion ofthe water to the crude oil and to independently control the agitatormotor in each reactor.
 3. The apparatus of claim 1, further comprising:a crude oil pump to pump the crude oil from a crude oil supply to thecrude oil inlet; and a water pump to pump the water from a water supplyto the water inlet, wherein the control circuit controls the proportionof the water to the crude oil by controlling the crude oil pump and thewater pump.
 4. The apparatus of claim 1, wherein the reactor furthercomprises a bucket and the agitator comprises a rotor at the bottom ofthe bucket, the agitation rate being a rotation speed of the rotor, andthe control circuit further controls the agitator motor to adjust aheight of the rotor above the bottom of the bucket.
 5. The apparatus ofclaim 1, further comprising a heating element to heat the reactor and atemperature sensor to sense a temperature of the reactor, wherein thecontrol circuit is further configured by logic or code to control thetemperature of the reactor by using the temperature sensor to sense thetemperature of the reactor and by using the heating element to heat thereactor in response to the sensed temperature.
 6. The system of claim 1,further comprising a nitrogen (N₂) gas inlet to supply N₂ gas to thereactor in order to provide anoxic conditions to the reactor during andafter the simulation.
 7. A method to simulate biocide performance incrude oil pipeline conditions, the method comprising: simulating atwo-phase crude oil pipeline in a reactor including a crude oil phaseabove a water phase; controlling, using a processing circuit, a flow ofthe water phase in the reactor by controlling an agitator motor of anagitator to drive a desired agitation rate of the agitator in order toagitate the water phase; supplying, through a crude oil inlet under thecontrol of the processing circuit, crude oil to the reactor for thecrude oil phase; supplying, through a water inlet under the control ofthe processing circuit, water to the reactor for the water phase toreach a desired proportion of the water to the crude oil supplied to thereactor; supplying, through a biocide inlet, biocide to the reactor;sampling, through a water sample outlet, the water phase of the reactor;holding, at each of a plurality of coupon holders, a corrosion coupon ata bottom of the agitated water phase of the reactor during thesimulation of the two-phase crude oil pipeline; removing and replacing,at each coupon holder, the held corrosion coupon during the simulation;sealing, using a ball valve for each coupon holder, the reactor duringthe removal and replacement of the corrosion coupon; and obtaining,using a height-adjustable dip tube, a mixed sample of the crude oilphase and the water phase of the reactor at an interphase region of thecrude oil phase and the water phase in the reactor.
 8. The method ofclaim 7, wherein the reactor further comprises a plurality of reactorseach with a respective agitator motor, controlling the flow of the waterphase comprises independently controlling the flow of the water phase ineach reactor by controlling the respective agitator motor to drive thedesired agitation rate of the agitator of the reactor, supplying thecrude oil to the reactor comprises independently supplying the crude oilto each reactor, and supplying the water to the reactor comprisesindependently supplying the water to each reactor to reach the desiredproportion of the water to the crude oil supplied to the reactor.
 9. Themethod of claim 7, wherein the reactor further comprises a plurality ofreactors each having a dedicated biocide inlet and a dedicated watersample outlet, supplying the biocide to the reactor comprisesindependently supplying, through the dedicated biocide inlet of eachreactor, the biocide to the reactor, and sampling the water phase of thereactor comprises independently supplying, through the dedicated watersample outlet of each reactor, the water phase of the reactor.
 10. Themethod of claim 7, wherein the reactor further comprises a bucket andthe agitator comprises a rotor at the bottom of the bucket, theagitation rate being a rotation speed of the rotor, and controlling themotor further comprises controlling the motor to adjust a height of therotor above the bottom of the bucket.
 11. The method of claim 7, furthercomprising supplying, through a nitrogen (N₂) gas inlet, N₂ gas to thereactor in order to provide anoxic conditions to the reactor during andafter the simulation.